The miniaturization, increased output and faster signal speeds of communication devices in recent years have led to greater flattening of films by CMP and increasing demands for greater heat resistance, mechanical properties, hygroscopicity, adhesion, moldability and high etching selection ratio, and particularly a low specific dielectric constant, for the insulating films (IMD: intermetal dielectrics, ILD: interlayer dielectrics, PMD: premetal dielectrics, etc.) of electronic products.
Most particularly, the micronization of wirings due required for increased integration of semiconductor electronic parts (devices) such as LSIs and the like has been accompanied by problems such as longer signal delay times as a result of increased interwiring capacities, and therefore efforts have been more actively directed toward achieving lower dielectric constants and shorter heat treatment steps, as well as greater heat resistance and mechanical properties of electronic part insulating materials.
This is because, generally speaking, the wiring signal propagation speed (v) and the specific dielectric constant (∈) of an insulating material in contact with a wiring material are in the relationship represented by v=k/√∈) (where k is a constant), and therefore in order to increase the signal propagation speed to reduce the wiring delay it is necessary to either increase the frequency range used or absolutely minimize the specific dielectric constant of the insulating material.
Low dielectric constant materials currently being implemented as such insulating film materials for mass production include SiOF films (by CVD) having specific dielectric constants of about 3.5, while organic polymers such as organic SOG (Spin On Glass) having specific dielectric constants of 2.6-3.0 are also being investigated. Porous materials with pores in the films have also been proposed as insulating film materials with even lower specific dielectric constants of less than 2.6, and research is actively progressing towards their application for LSI interlayer insulating films.
Another low dielectric constant material is borazine, having a molecular structure wherein benzene carbon atoms are replaced with nitrogen atoms and boron atoms, which is known to have a lower calculated dielectric constant than benzene. Borazine-containing silicon polymer thin-films are also known to have high heat resistance.